How do I glue moving ceramic tiles without removing them?

Question

There was a problem with the pipes under the floor, which resulted in several ceramic tiles being removed. At the moment these tiles are back in place. The problem is that 2 tiles next to them, that weren't completely detached, were glued back by injecting typical silicone under them. The problem is that now they balance a bit when we step on them.

The silicone method was suggested to me, and didn't work well. The tiles are being slowly taken off, moreover the tile grout cracked several days after because of that little movement.

My only idea is to inject some more silicon under the tiles, and fill the gaps using typical grout.

How can I glue these 2 tiles back without taking them off?

Note: There is a fair amount of silicone under the two detached tiles, there is no point in injecting tile grout.

Answer 1

Silicone is supposed to allow movement and give. I cannot really think of anything worse to glue tiles to a floor. You need to take the tiles off, scratch off the silicone and reattach them with thinset. After that you can grout.

If you keep applying the silicone you will keep getting the same result.

Answer 2

This will not help OP, but may help another person who has a similar issue with loosening tiles.

I've not done this, so people with experience can shoot me down.

What if, instead of silicon, you used a runny epoxy. Load it into a squeeze bottle

and inject it under the tile.

Notes on using epoxies. These come in a bewildering variety of viscosities and setting time. Lower viscosity = easier injection, but also it may run away from the fill point and leave voids. Shorter set times gives it less time to move to the wrong place, but is harder to work with.

Setting time can be increased by chilling the components, decreased by mixing them warm. With polyester resin (fiberglass) -15 F can change set up time from twenty minutes to several hours, and +10 can decrease it from 20 minutes to 5. (Learned the hard way doing field repairs on canoes) YOu can compensate some by changing the ratio of hardener to resin, but more than a few percent change results in weaker setup.

Viscosity also changes with temperature.

If you wanted to go this route, I'd test by making a 'floor' on a half sheet of plywood.

The ONLY reason to go to this much work is to avoid ending up with a patch in the floor that doesn't match the rest of the floor.